Postgresql 中文操作指南

45.7. PL/Perl Event Triggers #

可以使用 PL/Perl 编写事件触发器函数。在事件触发器函数中，哈希引用 $_TD 包含有关当前触发器事件的信息。$_TD 是全局变量，对于触发器的每次调用都会获取一个单独的本地值。$_TD 哈希引用的字段为：

PL/Perl can be used to write event trigger functions. In an event trigger function, the hash reference $_TD contains information about the current trigger event. $_TD is a global variable, which gets a separate local value for each invocation of the trigger. The fields of the $_TD hash reference are:

  • $_TD→{event}

    • The name of the event the trigger is fired for.

  • $_TD→{tag}

    • The command tag for which the trigger is fired.

将忽略触发器函数的返回值。

The return value of the trigger function is ignored.

以下是一个事件触发器函数示例，说明上述的部分内容：

Here is an example of an event trigger function, illustrating some of the above:

CREATE OR REPLACE FUNCTION perlsnitch() RETURNS event_trigger AS $$
  elog(NOTICE, "perlsnitch: " . $_TD->{event} . " " . $_TD->{tag} . " ");
$$ LANGUAGE plperl;

CREATE EVENT TRIGGER perl_a_snitch
    ON ddl_command_start
    EXECUTE FUNCTION perlsnitch();